Significance: Endoscopes represent electro-optical devices that are used to visualize internal body cavities. The specialized endoscopic procedure of the upper gastrointestinal tract from the esophagus down to the duodenum is called an esophagogastroduodenoscopy.
Aim: We bring our newly developed capsule endoscopy device as a promising alternative diagnostic method for visualization of the upper gastrointestinal tract.
Approach: Capsule endoscopy has become an attractive method that uses a tiny wireless camera to take pictures of the digestive tract. Existing esophageal capsule endoscopy does not allow a retrograde view of the esophagus while retrograde scanning can provide information on the esophageal pathology.
Results: In comparison to the existing esophageal capsule endoscopy, our system is much simpler and cheaper due to the need for fewer electronic devices. Moreover, its use is not limited by the capacity of the batteries used by existing capsule endoscopes. The new esophageal endoscopic system was created by combining the universal serial bus (USB) endoscope module with the thin power wires that are routed through the USB port to the computer.
Conclusions: The endoscope was tested on a volunteer without any side effects such as nausea, belching, and general discomfort. The examination of the patient is performed in a sitting position and the patient discomfort during the examination is minimal so it can be performed without anesthesia.
An optical fiber sensor consisting of short sample of experimental Hi-Bi optical fiber integrated between two single mode (SM) optical fibers is proposed and experimentally demonstrated. The experimental fiber consists of core with diameter equals 8.5 μm and the two side Stress Applied Part (SAP) of diameter 25 μm. The SAPs are made of Al-Ladoped silica. The birefringence of the fiber is 3.19·10-4. We measured spectral distribution of intensity at the output of the SM fiber as function of the analyzer's adjustment angle and the suitable position of the analyzer was determined. Then we applied the bodies with weights up to 100 g on the fiber for two significant positions of SAPs: SAPs were next to each other and above each other. Evaluation of the measurements were done by the peak-to-peak amplitude of optical power difference (in dB) of two measurement for which we determine the applied force (weight). The sensitivities were determined to be 0.081 dB/g for SAPs next to each other and 0.037 dB/g for second position of SAPs, respectively. From the results it follows that the sensor could be used not only for determination of lateral force but also for determination of applied force position.
Lab-on-a-fiber-tip-devices combine the different materials and different configurations (for example photonic structures) to optical fiber tips. We propose, fabricated and experimentally demonstrated a fiber tip device, the 3D polymer photonic structure of Fabry-Perot cavity integrated at the end of the optical fiber. Also, we prepared and experimentally demonstrated a fiber tip device with Bragg reflector integrated at the end of the optical fiber. Both structures, the Bragg’s reflector and the Fabry-Perot cavity, were created in IP Dip polymer cylinder with a diameter like a diameter of an optical fiber which is advantageous for integration. Layers of structures consist a material with refractive index 1.5 and air. In addition, a method of transferring and bonding of a photonic structure at the end of the optical fiber is described. In all investigated interval of wavelengths there is good agreement between measured and calculated reflection spectra.
In this paper we proposed new concept for fabrication of 3D polymer waveguides with surface Bragg grating (SBG). For the structures fabrication we used 3D laser lithography based on direct laser writing process with nonlinear two-photon absorption in photosensitive material. High-resolution negative IP-Dip photoresist for the structure fabrication was used. The 3D photonic structure consists of supporting structure and waveguide with SBG. To improve the light guiding properties, waveguide part was isolated from the supporting structure by thin polymer pillars. The SBG parameters were numerically proposed by transfer matrix method to reflect narrow spectral band at 1.55 μm wavelength. Design of the proposed structure is suitable as a sensor for on-chip application for measurement of temperature or refractive index. Reflection characteristics of the SBG waveguide were measured with direct edge optical fiber coupling by optical spectrum analyzer. Quality of prepared structure was investigated by scanning electron microscope.
A preparation of polydimethylsiloxane (PDMS) interferometer located at the end of a single-mode optical fiber is presented. For preparation of Fabry-Perot interferometer (FPI) we used the PDMS Sylgard 184 (Dow Corning). During fabrication process of FPI the length of micro-cavity in PDMS can be set to required size. After the setting the length of microcavity was fixed by encapsulating of another layer of PDMS. By measuring the transmission characteristic under the constant conditions of environments we observe a periodic change of signal depending on the wavelength – interference pattern. When the measurand is applied on FPI, PDMS changes its volume and also its refractive index resulting in a change in length of microcavity. The change of length of FPI modifies the interference pattern. For evaluation of influence of measurands change, we chose one maximum (wavelength of the maximum) as a reference wavelength at the reflected spectra. Then we changed the amount of measurand and we observed wavelength shift of the maximum and compared it with the wavelength of reference maximum of reflected spectra. We investigated the sensitivity of PDMS FPI on temperature and pressure. The dependencies to temperature and pressure have linear character. The temperature sensitivity of fabricated PDMS FPI is 5.76 nm/°C. In free spectral range of FPI it is possible to determine the difference of temperature 2.7 °C. After that 2π jump in reflected spectra occurs. The pressure sensitivity is -0.64 nm/kPa and free spectral range of FPI corresponds to 11 kPa.
Polymer based photonics brings simple and cheap solutions often with interesting results. We present capabilities of some siloxanes focusing on polydimethylsiloxane (PDMS) with unique mechanical and optical properties. In combination of laser lithography technologies with siloxane embossing we fabricate different grating structures with one- and two-dimensional symmetry. Concept of PDMS based thin membranes with patterned surface as an effective diffraction element for modification of radiation pattern diagram of light emitting diodes is here shown. Also the PDMS was used as an alternative material for fabrication of complicated waveguide with implemented Bragg grating. For lab-on-chip applications, we patterned PDMS microstructures for microfluidic and micro-optic devices.
The polysiloxane fibres made of polysiloxanes such as polydimethylsiloxane (PDMS) and poly(dimethyl)(diphenil)siloxane (PDMDPS) can be attractive for different fibre applications and fibre structures. In this paper we describe the fabrication technological process of polysiloxane fibres and fibre structures integrated with conventional single-mode optical fibres. We present two-modes interferometer prepared from PDMS biconical optical fibre taper, PDMDPS optical fibre microloop interferometer and liquid microdroplet optical fibre interferometer. We achieved interesting optical properties all these fibre structures as was confirmed from the transmission characteristics what may be attractive for utilisation in various types of optical fibre sensors.
We prepared and demonstrated a compact, simple-to-fabricate, air microcavity in polydimethylsiloxane (PDMS), placed at the end of a single-mode optical fiber. The air microcavity creates a Fabry-Perot interferometer. The length of microcavity changes with change of temperature. So the wavelength shift of reference minima (maxima) of interference pattern corresponds to temperature change. For the operation of the sensor broadband light source and low-resolution optical spectral analyzer can be used. The sensor response for change of temperature is fast and occurs within a few seconds. The temperature sensitivity is 6.1 nm/°C. For optical spectral analyzer resolution 0.1 nm the smallest temperature difference possible to determine is 0.017 °C.
We describe fabrication process of optical waveguide structures such as multi-mode optical splitter and optical waveguide with surface Bragg grating in polydimethylsiloxane (PDMS). Technology based on drawing of thin photoresist fiber with diameter up to 100 μm was developed and optimized. In this way, fibers drawn from photoresist form cores of waveguides in PDMS slab. After removal of the photoresist, created air channels can be filled in with different liquids. We prepared multimode waveguide structures in PDMS composed of two PDMS materials with different refractive indices. Using this technology, also complicated waveguide structures were prepared as optical splitter and surface Bragg grating were prepared in PDMS material.
The paper describes the preparation of polydimethylsiloxane (PDMS) fiber integrated on the conventional optical fibers and their use for optical fiber displacement sensor. PDMS fiber was made of silicone elastomer Sylgard 184 (Dow Corning) by drawing from partially cured silicone. Optical fiber displacement sensor using PDMS fiber is based on the measurement of the local minimum of optical signal in visible spectral range generated by intermodal interference of circularly symmetric modes. Position of the local minimum in spectral range varies by stretching the PDMS fiber of 230 μm in the wavelength range from 688 to 477 nm. In the stretched PDMS fiber is possible to determine the longitudinal displacement with an accuracy of approximately 1 micrometer.
In this paper, effect of two-dimensional photonic pattern on the properties of the GaAs/AlGaAs based light emitting
diode (LED) is demonstrated. The interference lithography was employed to surface patterning of the GaAs/AlGaAs
based LED. The active region of the LED includes a GaAs/AlGaAs triple quantum well emitting at 850 nm. Interference
lithography was used for preparation of two-dimensional pattern in the upper diode layer. The prepared LED with two-dimensional
patterned photonic crystal structure was then investigated by electrical and optical measurements. Prepared
photonic crystal LED shows enhanced light extraction efficiency due to the more effective extraction of guiding modes,
what was documented from finite difference time domain simulations as well as from L(I) measurements.
Proc. SPIE. 7746, 17th Slovak-Czech-Polish Optical Conference on Wave and Quantum Aspects of Contemporary Optics
KEYWORDS: Optical fibers, Lithography, Optical microscopes, Optical lithography, Gallium arsenide, Scanning electron microscopy, Photoresist materials, Near field scanning optical microscopy, Nanoimprint lithography, Near field optics
This contribution presents experimental results from the fabrication of planar photonic structures with two-dimensional
(2D) arrangement. We demonstrate the near-field scanning optical microscope (NSOM) lithography as an effective
optical method for fabrication of 2D photonic structures in thin photoresist layer. We employ a non-contact mode of
NSOM lithography using a metal coated fiber tip in combination with 3D nanoposition piezosystem. Prepared photonic
structures in thin photoresist layer deposited on the GaAs substrate are analyzed by scanning probe diagnostics. Set of
experiments was realized in order to improve the aspect ratio of the patterned structures, where the exposure time and the
intensity of the exposing field were parameters.
Proc. SPIE. 7746, 17th Slovak-Czech-Polish Optical Conference on Wave and Quantum Aspects of Contemporary Optics
KEYWORDS: Lithography, Optical lithography, Polymethylmethacrylate, Gallium arsenide, Photonic crystals, Photoresist materials, Near field scanning optical microscopy, Nanoimprint lithography, Group III-V semiconductors, Near field optics
This contribution presents experimental results in the field of planar two-dimensional (2D) photonic crystal (PhC)
structures, as well as their design, fabrication and analysis. We demonstrate maskless optical methods leading to
fabrication of 2D PhC structures for applications in optoelectronics. The 2D PhC structures of square and triangular
symmetries with period from 275 nm to 2 μm were fabricated in thin photoresist layer, III-V semiconductor surfaces and
polymethylmethacrylate using interference lithography and near-field scanning optical microscope lithography. The 2D
PhC structures prepared in GaAs surface were used as a mold for nanoimprint lithography in polymethylmethacrylate.
The equipment for intermodal interference investigation is described. The results of an investigation of intermodal
interference within a photonic crystal fibre (from Centaurus Technologies, Sydney) in terms of length and frequency
region are presented. From the measured values the difference of the phase constant of the fundamental and the first
higher order (antisymmetric) modes, as well as the decay constant of the mode in the wavelength region exceeding the
two modes region, are determined.
Intermodal interference in a photonic crystal fibre is measured in fibre samples of different lengths. The measurement was performed for attenuation of the first higher order mode determination. Also, the mode field distributions at the end of short and longer samples were measured. This measurement allows finding field distribution of the second mode.